Judy Lehmberg (FLC I) - Lee College

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degrees C. Beaker C had 10 ml of water boiled away. And during that same time, the 100 ml of water in Beaker A increased by _______________ degrees C. 4. How many calories of heat were required to evaporate the 10 ml of water in Beaker C? (Remember: You must consider both how much water is in Beaker A and how much its temperature increased while Beaker C boiled away.) _____________ calories. 5. So, how many calories would be required to evaporate only 1 ml of water? _____________ calories. 6.What does this exercise tell you about calories, exercise, and sweating? As you exercise your body temperature increases. Some of that heat can be released as water molecules leave your body. Practice 6 - What the Heck is pH? HYDROGEN IONS An ion is an atom that has lost or gained electrons, and thereby has become electrically charged (either + or -). They act differently than uncharged atoms. (It's like comparing magnets with nonmagnets.) These ions are very important in out life processes, and we would die without them. Table salt is an example of two essential ions -- sodium and chloride. Of all the ions in your body, none is more important than the hydrogen ion, H+. The term "pH" refers to the concentration of H+ ions in water. Biologists are interested in H+ concentration because it affects chemical reactions so greatly. A small change in this ion can dramatically affect life. Acid rain and stomach acid are two expressions of the concentration of H+ ions. Also, the blood of a human is so sensitive to H+ concentration that a small pH change from your normal of 7.4 can result in your death. We monitor the pH of our fish aquariums and our swimming pools in order to avoid potential problems. In the case of the aquarium, we are trying to maintain a good environment for micro-organisms, whereas, in the swimming pool, we are trying to prevent micro-organisms from growing. QUESTIONS: 1. Knowing how important pH can be to living organisms, what would be the effect of acid rain on the ecosystem? It can have devastating effects on organisms, especially aquatic organisms. There are many bodies of water that are now biologically dead due to low pH as a result of acid rain. 2. What does the "p" stand for in pH? Potential, it is the potential of hydrogen. The pH scale ranges from 1 to 14. Each step up the pH scale means that there is 10x more OH- (base) and less H+ (acid) than the step below. 34
Each step down the pH scale means that there is 10x more H+ (acid) and 10x less OH- (base) than the step above. A water solution with a pH of 7 is neutral because the concentration of the H+ ions (acid) is equal to the concentration of the OH- ions (base). If the pH is less than 7, then there are more H+ (acid) ions than OH- (base) ions, and the solutions is called an acid. If the pH is more than 7, then there are more OH- (base) ions than H+ (acid) ions, and the solution is called a base. QUESTIONS: 1. pH is a measure of hydrogen ion concentration. 2. A pH of 3 would be an acid or a base? an acid 3. A pH of 11 would an acid or a base? A base 4. What is the relationship between H + and OH- at a pH of 7? H + should equal OH - 5. How much more H + is in water at a pH of 3 when compared to a pH of 6? Water with a pH of 3 is 1000 times more acidic than water with a pH of 6. 6. How much more OH- is in water at a pH of 11 when compared to a pH of 7? Water with a pH of 11 is 10,000 times more basic than water with a pH of 7. HOW TO MEASURE PH The pH can be measured with a machine or with special color indicators. A pH machine directly reads the H+ concentration and displays the pH on a screen. A color indicator is a special molecule that changes color at a particular pH level. We will use the second technique -- pH color indicators --because they are a lot cheaper than the machine. GO GET: A pH paper test kit. NOW: 1. Use the pH paper test kit to determine the pH of the three unknown solutions on the demonstrations table. 2. Dip a separate pH test strip into the 3 solutions. 35
Page 1 and 2: BIOL 1406 - General Biology I Judy
Page 3 and 4: have an A average before the final
Page 5: Practice 1 - Critical Thinking Powe
Page 14 and 15: Comprehension - Level 2 - Understan
Page 16 and 17: Answer: They didn't understand it?
Page 18 and 19: 2. In order for the liquid water to
Page 20 and 21: 1. Weigh the piece of steel. 2. Put
Page 24 and 25: QUESTIONS: 1. Is solution A acid or

Judy Lehmberg (FLC I) - Lee College

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